The present invention relates generally to reusable launch vehicles. More particularly, the invention relates to a protective panel for a reusable launch vehicle having an outer ceramic matrix composite panel and an insulative bag assembly.
In the space transportation industry, recent trends have been toward developing space vehicles that have aircraft-like operability. The result has been the evolution of the reusable launch vehicle (RLV) to provide such operability. In order to fully realize the vision and potential of the RLV, a number of considerations relating to launch, reentry, and maintenance must be addressed. In response to many of these considerations, the typical RLV relies upon the thermal protection system (TPS) concept.
One approach to the modern day TPS involves the attachment of ceramic tiles and blankets to an outer surface of the RLV. There is room for improvement, however, with regard to the manner in which these tiles and blankets provide protection to the RLV. Typically, water molecules from the environment will penetrate the tile or blanket unless some form of moisture protection is provided. It is therefore common to inject the tile or blanket with a waterproofing compound that essentially coats the internal fibers to prevent xe2x80x9cwickingxe2x80x9d. This process involves the use of a considerable amount of materials and labor, which are both at a premium in the space transportation industry. Furthermore, the high temperatures associated with reentry of the RLV have a tendency to xe2x80x9cbakexe2x80x9d out the waterproofing compound such that re-waterproofing is required after each use. The re-waterproofing process can be extremely costly and time consuming. It is therefore desirable to provide a protective panel for an RLV that does not require waterproofing or re-waterproofing.
In recent years, metallic panels have been developed that partially address the above waterproofing concerns. There is considerable room for improvement, however, over these designs as well. For example, the metallic panels are typically made of nickel based alloys that will protect the RLV from temperatures around 1800xc2x0 F. (982xc2x0 C.). This temperature limitation has a direct relationship with the reentry profile for the RLV. Specifically, the lower temperature threshold associated with metallic tiles results in less efficient reentry profiles due to the need to minimize temperature elevations. Furthermore, the metallic tiles are significantly heavier than conventional ceramic tiles. It is therefore desirable to provide a protective panel for an RLV that is resistive to elevated temperatures and is relatively light weight.
It is also important to note that the dimensions of ceramic tiles are critical to avoid breakage. Thus, conventional ceramic tiles are typically 6xe2x80x3 by 6xe2x80x3 in size, with a 3xe2x80x3 maximum thickness. The relatively small size of these panels can add to manufacturing costs by requiring the fabrication of a higher number of panels. It is therefore desirable to provide a protective panel for a RLV that is larger in size than conventional panels.
The above and other objectives are provided by a protective panel for an RLV in accordance with the present invention. The protective panel includes an outer ceramic matrix composite (CMC) panel for isolating the RLV from elevated temperatures, and an insulative bag assembly coupled to the outer CMC panel. The insulative bag assembly isolates the RLV from moisture as well as elevated temperatures. A standoff attachment system attaches the outer CMC panel and the bag assembly to the RLV primary structure (e.g. tank wall). The use of CMC material for the outer panel provides the ability to withstand significantly higher temperatures as well as reduced weight. Furthermore, the waterproof insulative bag assembly eliminates the need for re-waterproofing.
Further in accordance with the present invention, an insulative bag assembly for an RLV protective panel is provided. The bag assembly includes a foil bag having a first opening shrink fitted to an outer panel such that the first opening and the outer panel form a water tight seal at temperatures below a desired temperature threshold. Fibrous insulation is contained within the foil bag for further protecting the launch vehicle from elevated temperatures. The bag assembly further includes a back panel coupled to a second opening of the foil bag such that the fibrous insulation is encapsulated by the back panel, the foil bag, and the outer panel.
The present invention also provides a method for fabricating an RLV protective panel. The method includes the steps of heating a foil bag and an outer CMC panel to a predetermined stretching temperature, where the stretching temperature defines a temperature threshold at which the foil bag expands to a circumference that is greater than the circumference of an attachment surface of the outer CMC panel. A first opening of the foil bag is then positioned around the attachment surface of the outer CMC panel. The method further provides for cooling the foil bag and the outer CMC panel to a predetermined shrinking temperature, where the shrinking temperature defines a temperature threshold at which the foil bag retracts to a circumference that is less than the circumference of the attachment surface.